(a) Field of the Invention
The present invention relates to an apparatus and method for transmitting a frame in a WAVE-based vehicle communication system.
(b) Description of the Related Art
WAVE (Wireless Access for Vehicular Environment) is a network for vehicle communication with interference such as a Doppler shift caused by high-speed travel, and supports vehicle-to-vehicle (V2V) communication and vehicle to infrastructure (V2I) communication installed between a vehicle and a road.
The WAVE uses 7 channels, i.e., multi-channels allocated for V2V and V2I in a frequency spectrum of 5.85 to 5.925 GHz (bandwidth of 75 MHz). One of the 7 multi-channels is a control channel CCH used for transmitting and receiving control information, and the other 6 channels are service channels SCHs used for traffic safety or general commercial services. At this time, if one physical layer PHY is used, communication can only be done using one channel. Accordingly, in the case of using one physical layer PHY, the multi-channels can be operated, divided into a CCH interval for using the CCHs and a SCH interval for using the SCH. Various control frames are transmitted and received between a vehicle and an infrastructure during the CCH interval, and service frames are transmitted and received between an infrastructure and a vehicle and between vehicles during the SCH interval.
A vehicle communication network supports QoS (Quality of Service) using a contention-based EDCA (Enhanced Distributed Channel Access) scheme. EDCA provides channel access priority according to user priority.
WAVE uses four queues of different priorities for CCH and SCH, respectively, to achieve contention-based EDCA transmission, and frames are transmitted with high channel access probability. By the way, in the event of any emergency frame that should be urgently transmitted in real time, such as an accident message or an urgent message, even if an emergency frame is allocated to a queue with high priority, a transmission delay occurs to the emergency frame if other frames are saved in the queue.
Moreover, even when there is no frame in the queue, transmission is possible only during a corresponding channel interval, and consequently a transmission delay occurs until a channel interval capable of transmission arrives. For example, in the case of an emergency frame which requires the use of a CCH channel, if the current channel interval is an SCH interval, a transmission delay of the emergency frame occurs until a CCH interval arrives.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.